Not Applicable
1. Field of the Invention
The present invention relates to a large volume golf club head that optimizes the products of moments of inertia. More specifically, the present invention relates to a large volume golf club head that has large moments of inertia with smaller absolute values for the products of inertia.
2. Description of the Related Art
In recent years, substantial attention has been directed toward the development of golf club heads having desired weight characteristics and, in particular, toward the development of golf club heads having a desired center of gravity location. For example, a designer may want to locate the center of gravity of a golf club head in a predetermined or preferred position relative to the face or xe2x80x9csweet spotxe2x80x9d of the golf club head to provide greater distance.
Because conventional golf club heads are typically made from metal alloys or other materials having a subhomogeneous density, the weight characteristics of such golf club heads are typically defined by their overall shape. Thus, to alter the location of the center of gravity of a golf club head, it is often necessary to redesign the shape or configuration of the golf club head. However, this may adversely impact other desired characteristics of the golf club head.
The design process may be further complicated where golf club heads are manufactured using composite materials (typically carbon reinforced plastic). Because composite materials are typically less dense than metal and other conventional materials, composite golf club heads generally require additional weighting to achieve desired swing weights for finished golf clubs.
The Rules of Golf, established and interpreted by the United States Golf Association (xe2x80x9cUSGAxe2x80x9d) and The Royal and Ancient Golf Club of Saint Andrews, set forth certain requirements for a golf club head. The requirements for a golf club head are found in Rule 4 and Appendix II. A complete description of the Rules of Golf are available on the USGA web page at www.usga.org. Although the Rules of Golf do not expressly state specific parameters for a golf club, Rule 4-1 d states that the club head shall be generally plain in shape, and all parts shall be rigid, structural in nature and functional.
In the past few years, the volume of drivers and fairway woods have increased to provide greater forgiveness for golfers. The BIG BERTHA(copyright) driver from Callaway Golf Company of Carlsbad, Calif., at 195 cubic centimeters (cc) was the beginning of the large volume drivers. The BIG BERTHA(copyright) stainless steel driver was followed by the GREAT BIG BERTHA(copyright) titanium driver, also from the Callaway Golf Company, which had a volume of 250 cc. Then, the BIGGEST BIG BERTHA(copyright) titanium driver was introduced by the Callaway Golf Company, which had a volume of 295 cc. Recently, the forged titanium ERC(copyright) driver was introduced by the Callaway Golf Company, which had a volume of 300 cc. These large volume drivers have greater moments of inertia than previous golf clubs partly due to their size, and the desire to locate the center of gravity in a favorable position. It was believed that increasing the moments of inertia, Ixx, Izz and Iyy, of a driver would make the driver more forgiving. However, forgiveness, in the form of reduced dispersion is not a function of the moments of inertia, but rather a result of the products of inertia, Ixy, Ixz and Iyz.
The products of inertia relate moments about one axis with head rotations about another axis. These head rotations in turn cause vertical or horizontal gear effect that impart increased or reduced backspin and draw or fade spin to a golf ball. Unlike the spins generated by conventional gear effect associated with Iyy and Izz, these spins cannot be compensated for by adjusting the face bulge radius and the face roll radius. As club heads become larger than 300 cc, and moments of inertia become larger, Izz greater than 3000 grams centimeter squared and Iyy greater than 1800 grams, there is a propensity for the products of inertia to also become larger. As the products of inertia become larger, there is a deleterious effect on dispersion.
Thus, there is a need for a large volume golf club head with large moments of inertia, that have smaller products of inertia. This need is difficult to meet since large products of inertia are by-products of large moments of inertia.
The present invention provides a large volume golf club head with high moments of inertia that has smaller products of inertia. The golf club head of the present invention provides all of the advantages of large volume golf club heads with large moments of inertia, such as greater confidence and greater distance, without the attendant increase in dispersion. Thus, off-center hits have greater distance and increased straightness with the golf club head of the present invention, which results in more consistent golf ball flight and improved accuracy for the golfer.
One aspect of the present invention is a golf club head including a body having a crown, a sole and a striking plate. The body has a hollow interior. The golf club head has a moment of inertia, Izz, about a vertical axis Z through the center of gravity of the golf club head that is greater than 3000 g-cm2. The golf club head also has a moment of inertia, Iyy, about the horizontal axis Y through the center of gravity of the golf club head that is greater than 1900 g-cm2. Each of the products inertia, Ixy and Ixz, of the golf club head has an absolute value less than 100 g-cm2, and the product of inertia Iyz is greater than 0 g-cm2.
Another aspect of the present invention is a golf club head having a body composed of a titanium, titanium alloy, steel, stainless steel, or amorphous material. The body has a crown, a sole, a ribbon, a striking plate and a hollow interior. The golf club head has a volume ranging from 300 cm3 to 600 cm3. At least one weight member is disposed within the hollow interior of the body along the ribbon. The golf club head has a moment of inertia, Izz, about a vertical axis Z through the center of gravity of the golf club head that ranges from 3000 g-cm2 to 5000 g-cm2. The golf club head has a moment of inertia, Iyy, about the horizontal axis Y through the center of gravity of the golf club head that is at least 1900 g-cm2. Each of the products inertia, Ixy and Ixz, of the golf club head has an absolute value less than 100 g-cm2, and the product of inertia Iyz ranges from 0 g-cm2 to 300 g-cm2.